Natural heart valves, such as aortic valves, mitral valves, pulmonary valves and tricuspid valves, can become damaged by disease in such a manner that they fail to maintain blood flow in a single direction. A malfunctioning heart valve may be stenotic (i.e., heart leaflets are closed down) or regurgitant (i.e., heart leaflets are wide open). Maintenance of blood flow in a single direction through the heart valve is important for proper flow, pressure and perfusion of blood through the body. Hence, a heart valve that does not function properly may noticeably impair the function of the heart.
Cardiac valve prostheses are well known in the treatment of heart disease to replace malfunctioning heart valves. Heart valve replacement previously required open-heart surgery with its attendant risk, expense, and extended recovery time. Open-heart surgery also requires cardiopulmonary bypass with risk of thrombosis, stroke and infarction. For some patients, open-heart surgery is not even an option because of a critical condition, advanced age, co-existing infection, or other physical limitations.
Recently, there has been increasing interest in minimally invasive and percutaneous replacement of cardiac valves, typically by way of catheterization. In minimally invasive procedures, a catheter is used to insert a valve in a lumen of a blood vessel via percutaneous entry through a distal blood vessel. Typically, such percutaneous prosthetic valve devices comprise an expandable stent segment, a stent anchoring segment and a flow-regulation segment, such as a biological valve. The expandable stent portion is either self-expandable or expanded using a balloon that is part of a transcatheter delivery system.
A drawback of using a stented valve is that the stent can be difficult to properly position, resulting in a misplaced valve. Additionally, stented valves may also lack sufficient radial strength, which could cause migration after implantation due to forces applied by the blood surrounding the valve in the heart. Therefore, there is a need for improved heart valve prostheses that may be implanted using minimally invasive techniques.